1. Field of the Invention
The present invention relates generally to weaving and more particularly to an adjustable reed capable of tailoring the fill yarn angle and width of woven fabrics.
2. Description of the Related Art
The traditional role of the reed in the weaving of net-shaped fabrics is to tailor the fill yarn angle, control the width of the fabric and beat the fill yarn into the fell of the fabric. Increased flexibility in the design and fabrication of fabrics could be obtained if the ability to control the location of each reed wire were achieved. Conventional reeds, including fixed reeds and width adjustable reeds offer some flexibility in fabrication, but are still severely limited.
Fixed reeds such as fan reeds, in which the shape of the reed is unalterable, typically have been used to tailor fabric width. However, the fixed reed constrains the tailoring of fabric width based upon the fixed reed's original shape since the location of the warp yarn is set by the design of the reed. This makes use of such reeds impracticable or impossible in applications where the design requires a high level of tailorability. Even where it is possible to produce the desired fixed reed geometry, the reed may only be applicable to that specific application. Producing new reeds for each application is expensive and time consuming especially when prototyping a new structure where a design may still be in a state of flux. Adjustable width reeds are known, but offer only limited variations in reed spacing. U.S. Pat. No. 5,067,215 to Behl et al. discloses an expanding reed comprised of a number of hinged points which can be moved in a guide to uniformly pull apart the individual reed teeth to a greater or lesser extent to change the width of a yarn sheet. U.S. Pat. No. 5,158,116 to Kazuo et al. discloses several means for moving dents toward and away from each other, including: 1) a guide plate with a pattern of elongated slits to guide the dents, 2) an expander in which individual dents are mounted to crossing portions, and 3) an elastic member to which individual dents are attached at equal intervals.
The ultimate in tailorability of fill yarn angle and fabric width would require the ability to dynamically change the location of each individual reed wire during the weaving process. However, for most structural applications it would be more practical to control the position of groups of reed wires. In the present invention, reed wires are grouped and each group can be moved parallel and perpendicular to the warp yarns. The profile of the reed wires within the groups can be skewed to tailor fill yarn fiber angle and the reed wires within each group can be simultaneously spread or contracted to locally control fabric width. In addition, the spacing between reed groups can be individually varied. This dual capability to vary fill yarn angle and fabric width does not exist in typical fixed reeds or adjustable width reeds. Presently, if variations of width or fill yarn angle are desired in a finished article it is generally necessary to exchange reeds or halt the production to adjust the reed.
The tailorability possible with the present invention may offer benefits in the fabrication of a variety of materials. Laminated composite materials have typically been difficult to fabricate because they exhibit many unique failure modes. Delamination induced failures initiated at the free edge of the composite laminate are frequently produced. This failure is created from the high interlaminar stresses that only occur adjacent to the free edge. The creation and magnitude of these interlaminar stresses near the free edge can be partially attributed to the mismatch in Poisson's ratio between adjacent layers of material having different fiber orientation. The ability to tailor the fiber angle in each layer near the free edge could result in a significant reduction in the magnitude of these interlaminar and intralaminar stresses. Utilizing the adjustable reed of the present invention, it will be possible to readily tailor the fiber orientation of each layer at the free edge.
An adjustable reed with the ability to control the fiber angle and fabric width dynamically during the weaving process greatly increases the level of tailoring that is achievable by facilitating the simultaneous local tailoring of fill yarn angle and fabric width along the length of the fabric. This adjustability results in higher levels of structural efficiency and reduced structural cost through more optimal use of materials and the elimination of the need for secondary steps such as cutting. An adjustable reed will also significantly reduce material prototyping cost because new reeds will not have to be produced for each design and through reducing setup time required to redraw the warp yarns through the loom.